Apparatus and Method for Filter Manufacture

ABSTRACT

A filter rod for a smoking article comprising an extruded hardened tubular element formed from a filter material with entrained cured plasticiser, and a continuous core of filler material provided within the tubular element. Also disclosed is an apparatus for manufacturing such a filter rod, the apparatus comprising a duct having an inlet to receive filter tow material and plasticiser, and an outlet. The duct tapers between the inlet and the outlet. A mandrel is disposed at least partially within the duct and is fixed relative to the duct. The mandrel is hollow and includes an internal passage extending though the mandrel through which a filler material may be conveyed. The passage includes an outlet at a distal end of the mandrel though which the filler material may be expelled. A heating zone is configured to heat filter material. The apparatus is configured such that filter tow material and plasticiser conveyed through the duct is compressed around the mandrel into a tubular rod, and filler material fed though the internal passage of the mandrel is expelled out of the passage outlet to fill the bore of the tubular rod. The tubular rod is heated in the heating zone to at least partially cure the plasticiser, to produce a continuous filter rod comprising a tubular rod of hardened filter material with a continuous core of filler material. Also disclosed is a method of manufacture of such a filter rod.

TECHNICAL FIELD

In this specification there is described an apparatus and method for filter manufacture and, in particular, an apparatus and method for manufacture of filters with a filled core for use with smoking articles.

BACKGROUND

Apparatuses and methods for manufacture of smoking article filters are known that comprise a continuous garniture belt that conveys filter tow material fed onto a continuous band of plug wrap though a tapering garniture duct or “tongue”. Within the garniture tongue the garniture belt wraps the plug wrap around the filter tow material and compresses the material into a continuous cylindrical wrapped rod which can subsequently be cut to desired lengths.

SUMMARY

In this specification there are described embodiments of a filter rod for a smoking article comprising an extruded hardened tubular element formed from a filter material with entrained cured plasticiser, and a continuous core of filler material provided within the tubular element.

The filter material may comprise cellulose acetate tow which is hardened with a plasticiser. The filter rod preferably does not comprise any outer wrap around the tubular element.

The filler material of the core may comprise cellulose acetate, and in an embodiment, may comprise a granular aerosol modifying material. In an alternative embodiment, the filler material may comprise tobacco or a derivative of tobacco.

The present invention also provides a filter for a smoking article comprising a filter rod as described above, and a second filter segment axially aligned with the filter rod and joined thereto by a plug wrap around the filter rod and second filter segment.

The present invention also provides a smoking article comprising a tobacco rod and a filter rod or filter as described above, joined to one end of the tobacco rod.

The present invention also provides an apparatus for manufacturing an extruded filter rod for smoking articles, the apparatus comprising a duct having an inlet configured to receive filter tow material and plasticiser, and an outlet, the duct tapering between the inlet and the outlet, a mandrel disposed at least partially within the duct and fixed relative to the duct, wherein the mandrel is hollow and includes an internal passage extending though the mandrel through which a filler material may be conveyed, the passage including an outlet at a distal end of the mandrel though which the filler material may be expelled, and a heating zone configured to heat filter material, the apparatus configured such that filter tow material and plasticiser conveyed through the duct is compressed around the mandrel into a tubular rod, and filler material fed though the internal passage of the mandrel is expelled out of the passage outlet to fill the bore of the tubular rod, and the tubular rod is heated in the heating zone to at least partially cure the plasticiser, to produce a continuous filter rod comprising a tubular rod of hardened filter material with a continuous core of filler material.

The internal passage of the hollow mandrel may include a tapered section which narrows in a direction towards the distal end of the mandrel.

The outer dimension of the hollow mandrel may include a tapered section which narrows in a direction towards the distal end of the mandrel.

A distance between an outer surface of the mandrel and an inner surface of the duct may reduce along at least a part of the length of the duct in a direction towards the distal end of the mandrel.

The distal end of the mandrel may be positioned downstream of the outlet of the duct. The mandrel may extend entirely through the length of the duct. Alternatively, the distal end of the mandrel may be positioned within the duct. The mandrel may extend into the heating zone.

The duct may comprise first and second sections, wherein the first section tapers from the inlet to the second section, and the second section is of constant cross-section, and wherein the distal end of the mandrel is disposed within the second section.

The distal end of the mandrel may be disposed within the heating zone.

The mandrel may be disposed coaxially with the duct.

The heating zone may comprise a steam supply to heat the filter material and plasticiser. The heating zone may include a steam chamber formed around a section of the duct, and the duct may include steam vents to allow steam supplied to the steam chamber to pass into the duct to directly heat the filter material.

The apparatus may further comprise a post-curing treatment station downstream of the heating zone with respect to the conveyance direction of the extruded continuous filter rod, and the post-curing treatment station may be configured to further smooth the outer surface of the extruded continuous filter rod.

The post-curing treatment station may comprise an electrical heater configured to heat the outer surface of the continuous filter rod. The electrical heater may be configured to heat the outer surface of the continuous filter rod to between 100-200 degrees Celsius.

The post-curing treatment station may be configured to melt the plasticiser on the outer surface of the continuous filter rod so that the melted outer surface can subsequently set as a smooth finish.

The post-curing treatment station may comprise a spray-coating station including a spray nozzle and a source of liquid treatment connected to the spray nozzle to spray the liquid treatment onto the outer surface of the continuous filter rod to form a smooth outer coating. The liquid treatment sprayed from the spray nozzle may comprise a plasticiser, and may comprise triacetate.

The apparatus may further comprise a cutting station configured to cut the continuous extruded filter rod into discrete filter rods.

The present invention also provides a method of manufacturing extruded filters for smoking articles, the method comprising feeding filter tow material and plasticiser into an inlet of a duct, the duct tapering between the inlet and an outlet, conveying the filter tow material through the duct and around a hollow mandrel disposed at least partially within the duct and fixed relative to the duct, such that the filter material is compressed into a tubular rod, conveying a filler material along an internal passage extending through the hollow mandrel, expelling the filler material from an outlet of the internal passage at a distal end of the mandrel to fill the bore of the tubular rod with the filler material, and heating the tubular rod to at least partially cure the plasticiser to produce a continuous filter rod comprising a tubular rod of hardened filter material with a continuous core of filler material.

The method may comprise expelling the filler material from the internal passage outlet at the distal end of the mandrel downstream of the outlet of the duct. The method may comprise expelling the filler material from the internal passage outlet at the distal end of the mandrel within the duct, upstream of the duct outlet.

The method may comprise heating the filter material and plasticiser in a heating zone of the apparatus using steam.

The method may comprise heating the filter material in the heating zone to at least partially cure the plasticiser before filling the bore of the tubular rod with the filler material.

The method may comprise compressing the filter tow material to at least partially form the tubular rod before filling the bore of the tubular rod with the filler material.

The method may comprise providing cellulose acetate tow as the filler material.

The method may comprise providing a pre-formed filter rod through the mandrel as the filler material.

The method may comprise providing tobacco as the filler material.

The method may further comprise performing a post-curing treatment on the continuous filter rod to provide the continuous filter rod with a smoother outer surface than the surface texture present when expelled from the heating region.

The post-curing treatment may comprise heating the outer surface of the continuous filter rod with an electrical heater and smoothing the outer surface.

The post-curing treatment may comprise heating the outer surface sufficiently to melt the plasticiser on the outer surface of the continuous filter rod and subsequently setting the melted outer surface as a smooth finish.

The method may comprise heating the outer surface of the continuous filter rod to between 100-200 degrees Celsius.

The post-curing treatment may comprise spray-coating a liquid treatment onto the outer surface of the continuous filter rod to form a smooth outer coating, and may comprise spraying a plasticiser, which may comprise triacetate, onto the outer surface of the continuous filter rod.

The method may further comprise cutting the continuous extruded filter rod into discrete filter rods.

BRIEF DESCRIPTION OF THE DRAWINGS

Embodiments will now be described, by way of example only, with reference to the accompanying drawings, in which:

FIG. 1 schematically shows a cross-section of a first embodiment of an apparatus for manufacturing filter rods;

FIG. 2 shows an enlarged view of a first portion of the apparatus shown circled in a dashed line in FIG. 1;

FIG. 3 shows an enlarged view of a second portion of the apparatus shown circled in a dashed line in FIG. 1;

FIG. 4 shows a cross-section through the apparatus of FIGS. 1 and 2 along the line X-X;

FIG. 5 shows a cross-sectional view along the line Y-Y as shown in FIG. 1, of a first embodiment of a filter rod manufactured using the apparatus of FIG. 1;

FIG. 6 shows a first embodiment of a smoking article including a filter made from a filter rod shown in FIG. 5;

FIG. 7 shows a cross-sectional view of a second embodiment of a smoking article including a filter made from a filter rod shown in FIG. 5;

FIG. 8 schematically shows a cross-section of a second embodiment of an apparatus for manufacturing filter rods; and

FIG. 9 shows a cross-sectional view along the line Z-Z as shown in FIG. 8, of a second embodiment of a filter rod manufactured using the apparatus of FIG. 8.

DETAILED DESCRIPTION

Referring now to FIG. 1, an apparatus 10 of a first embodiment is shown for the manufacture of filter rods and comprises a duct 11 having an inlet 12 and an outlet 13. The duct 11 comprises a first section 11 a that is circular in cross-section and that narrows from the inlet 12 to an intermediate point 15, and a second section 11 b of constant circular cross-section extending from the intermediate point 15 to the outlet 13. A source of compressed air (shown by arrows ‘C’) is provided to the duct 11 via compressed air ports 14 which, in use, helps propel filter tow material 16 into and through the duct 11.

A mandrel 17 is disposed within the duct 11 and comprises an elongate cylindrical member with a hollow passage 18 extending in an axial direction through the centre of the mandrel 17. The passage 18 includes an inlet 18 a at a proximal end of the mandrel and an outlet 18 b at the opposite, distal end of the mandrel 17. The mandrel 17 extends through both the first section 11 a and second section 11 b of the duct 11. The distal end of the mandrel 17 is disposed beyond the outlet 13 of the duct 11. The mandrel 17 is fixedly secured in the apparatus 10 so as to be fixed relative to the duct 11.

The second section 11 b of the duct 11 has a central bore 19 which is circular in cross-section, as can be seen from FIG. 4. The cross-section of the bore 19 of the second section 11 b of the duct 11 is constant along its length.

A heating zone 20 is provided in combination with and around a portion of the second duct section 11 b. The heating zone 20 comprises a closed chamber 21 around the second duct section 11 b with steam inlets 22. The second duct section 11 b includes a plurality of steam vents 23 which, in use, allow steam provided to the chamber 21 to pass into the bore 19 of the second duct section 11 b. A source of dry steam (not shown) is connected to the steam inlets 22 to supply hot dry steam to the chamber 21.

A cutting station 24 is provided downstream of the outlet 13 of the duct 11 and includes a cutting blade 25.

In use, filter tow material 16, such as cellulose acetate tow mixed with a plasticiser, is fed into the inlet 12 of the duct 11. The filter material 16 is mixed with the plasticiser, such as triacetate, in a ratio of about 17% by weight, although other ratios of plasticiser may be used within the scope of the invention, such as between 4% and 50% by weight. The filter tow with entrained plasticiser is conveyed through the first duct section 11 a using jets of compressed air provided through the compressed air ports 14. The tow material 16 passes around the mandrel 17 and is compressed into a cylindrical filter rod 26 as it passes through the tapering first duct section 11 a. The tow material 16 is formed around the mandrel 17 and is thereby compressed into a tubular filter rod 26 with a hollow core. Simultaneously, a filler material 27 is fed into the open end 18 a of the passage 18 of the mandrel 17 and is conveyed through the passage 18. This filter rod 26 being formed of the filter tow material 16 compressed around the mandrel 17 containing the filler material 27 is shown in cross-section in FIG. 4.

As the tubular filter rod 26 passes through the second duct section 11 b around the mandrel 17, dry steam at around 170 degrees Celsius is supplied to the chamber 21 and passes through the steam vents 23 and into the filter rod 26. The steam permeates and heats the filter rod 26. The filter rod 26 is also heated by being in contact with the second duct section 11 b which itself is heated by the steam. The supplied heat cures or substantially cures the entrained plasticiser in the filter tow material 16 so that the continuous filter rod 26 hardens to form a stiff continuous filter rod. The hardened continuous filter rod exits the heating zone 20 and exits the duct 11 through the outlet 13.

The filler material 27 is conveyed through the passage 18 in the mandrel 17 and is expelled out of the outlet 18 b into the hollow core of the filter rod 26. This results in a hardened continuous filter rod 28 with a continuous core of filler material 27

After the hardened continuous filter rod 28 exits the outlet 13 of the duct 11, it passes to the cutting station 24 where the cutting blade 25 cuts the hardened continuous filter rod 28 into individual lengths of discrete filter rods 29 having a continuous core filled with the filler material 27. These may be single length filter rods 29 of a size suitable for use in combination with a single tobacco rod to make a single smoking article. Alternatively, the discrete filled-core filter rods 29 may be “2-up”, “4-up” rods, or other lengths which are a multiple of a single length filter that would be joined to a tobacco rod in a finished smoking article. Such multiple length filters can be supplied to subsequent smoking article manufacturing machinery to be cut to length in later processing steps.

A discrete core-filled filter rod 29 of the invention manufactured using the above-described apparatus and method is shown in cross-section in FIG. 5. The filter rod 29 is substantially cylindrical and is continuous in cross-section along its length. The filter rod 29 comprises an outer tubular section 30 of hardened tow material 16, and core 31 of the filler material 27.

The core-filled filter rods 29 manufactured using the above-described apparatus and method are sufficiently stiff and strong not to require any outer plug wrap layer to be applied to maintain their shape and structural integrity. As such, the filter rods 29 can be provided directly to a subsequent smoking article manufacturing process and the absence of requiring an outer plug wrap means the manufacturing process is simpler, quicker, more efficient and more cost effective than known filter manufacturing processes where a subsequent filter rod wrapping step is performed, which requires additional machinery and materials. The filter rods 29 are also able to be manufactured to be accurately symmetrical about their central axis, that is, accurately circular in cross-section. This is at least in part because any oval distortion which may be caused by overlapping plug wrap seams of known wrapped filters is avoided.

FIG. 6 shows one exemplary configuration of a smoking article 40 incorporating a discrete filter rod 29 as described above. (Although, as described above, in a smoking article the filter segment may be a section cut from a multiple length filter rod 29, the filter rod segment within the smoking article 40 will be referred to herein as “filter rod 29”). The smoking article 40 comprises a tobacco rod 41 with a filter rod 29 abutting one end of the tobacco rod 41 and joined thereto by a tipping wrapper 42 which overlies the join between the tobacco rod 41 and the filter rod 29. In the exemplary smoking article 40, ventilation holes 43 are provided to allow ambient air to be drawn into the filter rod 29 for increased ventilation as a user draws on the smoking article 40 in use. Also in the exemplary smoking article 40, the core 31 is visible at the end of the smoking article 40. This can provide a visual indicator to a consumer of the type of smoking article 40 and its associated filter performance and/or flavour.

In one embodiment, the filler material 27 fed into the inlet 18 a of the passage 18 of the mandrel 17 may be a loose filter tow material, such as cellulose acetate. The loose tow material may be conveyed under pressure or force through the passage 18, and/or may be pulled through the mandrel 17 by conveyance of the downstream outer filter material 16 with which it is encircled. The passage 18 may be configured to taper towards the outlet 18 b, such that the tow material is compressed as it is conveyed through the passage 18. The core 31 of the resulting continuous filter rod 28 thereby may comprise a compressed filter tow material. The filter tow material comprising the filler material 27 may comprise an entrained plasticiser, which may comprise triacetate, and which may be in the proportions by weight mentioned above. However, different proportions may be used. In particular, a lower proportion of plasticiser may be used in the filler material such that the core 31 of the filter rods 29 are softer and more permeable to smoke drawn through the filter rod 19 than the outer tubular section 30.

The mandrel 17 extending entirely through the duct 11 may advantageously enable curing or part-curing of the filter tow material 16 within the duct 11 without the heat affecting the filler material 27 within the passage 18 of the mandrel 17. Also, the tubular filter rod 26 may be at least partially hardened before the filler material 27 is introduced into its hollow core. However, the invention is not intended to be limited to the embodiment shown in which the mandrel 17 extends entirely through the duct 11. In an alternative embodiment, the distal end of the mandrel 17 may be disposed within the duct 11 upstream of the outlet 13. In such an embodiment, the filler material 27 would be expelled into the hollow core of the tubular filter rod 26 within the duct 11. The distal end of the mandrel 17 may be disposed within the heating zone 20, or may be disposed downstream of the heating zone 20 but upstream of the outlet 13 of the duct 11.

The core filler material 27 being fed under pressure and/or being a compressed material, may advantageously facilitate formation of the continuous filter rod 26 into a desired shape. This results from the compressed filler material 27 exerting an outward force on the surrounding filter tow material 16 that forms the outer tubular section 30. In particular in the alternative embodiment described above in which the distal end of the mandrel 17 is disposed within the duct 11, this force helps press the filter tow material 16 against the inner wall of the bore 19 of the second duct section 11 b and so encourages the filter tow material 16 to harden in close conformity with the inner wall of the duct 11. This also helps press flat the fibres of the filter tow material 16 on the outer surface of the continuous filter rod 26, helping improve the roundness and smoothness of the resulting hardened filter rods 29.

In an alternative embodiment of the invention, the filler material 27 may be a smoke modifying material and may comprise, for example, a granular material such as flavourant or activated charcoal. These could be provided exclusively as the filler material 27 or may be entrained in a carrier material, for example, entrained in cellulose acetate tow. Furthermore, the filler material 27 may include an entrained flavourant. The flavourant may be provided as a solid particulate material such as flavourant granules, or may be provided as a liquid absorbed into a carrier material such as cellulose acetate tow.

In any of the above-described embodiments of the invention, if the filler material 27 comprises a filter material such as cellulose acetate tow, the tow of the filler material 27 may be the same composition than the tow of the filter material 16 that forms the outer tubular section 30 or may be of a different composition. If the filler material 27 is a cellulose acetate tow of a different composition, this may provide the core 31 with a different filtering characteristic to the outer tubular section 30. For example, the core 31 may have a greater or lesser draw resistance than the outer tubular section 30. The relative draw resistance of the core 31 and outer tubular section 30 may be chosen to control the amount of smoke that, in use, is drawn through each part of the filter rod 29. For example, if the core 31 has a lower draw resistance than the outer tubular section 30, a larger proportion of the smoke stream may flow through the core 31 than through the outer tubular section 30. This proportion can thereby be controlled to determine, for example, the amount of flavourant that may be entrained in the smoke stream, or the proportion of the smoke stream that passes over activated charcoal granules. An increased level of plasticiser and hardening of the outer tubular section 30 can give an increased draw resistance to the outer tubular section than that of the inner core 31.

In an exemplary embodiment, the outer tubular section 30 may comprise cellulose acetate with 10-20% plasticiser by weight, and the core may comprise cellulose acetate with plasticiser in 3-8% by weight.

The outer tubular section 30 being hardened provides smoking articles 40, 50 with structural strength during smoking by a consumer. This can help avoid deformation of the filter during smoking, and also provide tactile resistance to any “chewing” action of the consumer on the filter during smoking.

In an alternative embodiment of the invention, the filler material 27 may comprise tobacco or reconstituted tobacco. The tobacco filler material may thereby impart a tobacco flavour to the proportion of the smoke stream that passes through the core 31 of the filter rod 29.

In a further embodiment of the invention, the filler material 27 may be coloured and thereby may contrast with the filter tow material 16 of the outer tubular section 30. This may provide a user with a visual indicator of the filter and/or flavour properties of the filter rod 29. For example, a filler material 27 with a menthol flavour may be coloured green. Furthermore, a range of smoking articles may be provided that offer a range of smoking properties, for example differing filtering properties of flavour types or strengths. The core 31 of the filter rods 29 of such various different smoking articles may be coloured in different shades of a particular colour, or different colours, to indicate said different properties. Coloured filler material 27 of the core 31 may also reduce colouring of the filler material 27 during smoking of the smoking articles 40, 50, by disguising or at least partially concealing discolouration caused by smoke constituents entrained in the smoke drawn through and retained by the filter. This may be advantageous in an embodiment in which the draw resistance of the core 31 is lower than the draw resistance of the outer tubular section 30, such that a major proportion of the smoke drawn through the filter is drawn through the core 31.

In the smoking article 40 described above, a single discrete filter rod 29 is provided abutting the tobacco rod 41 and so the core 31 of the filter rod 29 is visible at the mouth-end of the smoking article 40. The may provide the advantages described above. However, alternative embodiments of smoking articles are envisaged incorporating the above-described core-filled filters. Such smoking articles may include multi-segment filters. A second embodiment of smoking article 50 is shown in cross-section in FIG. 7. Like features with the first embodiment of smoking article 40 retain the same reference numerals. The smoking article 50 of the second embodiment comprises a multi-segment filter 51 which comprises a first filter segment 29 as per the filter rod 29 described above, and a second filter segment 52 adjacent the first filter segment. The second filter segment 52 comprises a plug of a material such as cellulose acetate, preferably without an entrained particulate additive or core of different filler material.

A plug wrap 53 extends around the first and second filter segments 29, 52. The filter 51 is joined to a tobacco rod 41 by a tipping wrapper 42. The filter 51 is arranged such that the second filter segment 52 is disposed at the mouth-end of the smoking article, and the first filter segment 29 is disposed between the second filter segment 52 and the tobacco rod 41. The smoking article 50 of the second embodiment may be advantageous in the case where the core 31 of the first filter segment 29 comprises a particulate material, either entrained in a carrier material as described above, or exclusively as the core material. For example, if the core 31 comprises tobacco or charcoal granules entrained in cellulose acetate tow. In such case, the second filter segment 52 prevents the particulate material from coming out of the core 31 of the first filter segment 29 and into a user's mouth when a user draws on the smoking article 50 in use. It may also provide the mouth-end of the smoking article 50 with a conventional appearance, namely a filter end with a plain end face of continuous filter material. This may be beneficial to enable provision of improved filtering and/or flavour delivery functions using a core-filled filter as described above, without presenting the consumer with a visually different smoking article to that of their regular preferred smoking articles.

An apparatus 110 of a second embodiment is shown in FIG. 8 and is similar to the apparatus 10 of the first embodiment. Like features between apparatuses 10, 110 of the first and second embodiments retain the same reference numerals and detailed description will not be repeated. A difference with the apparatus 110 of the second embodiment is that the apparatus 110 includes a post-curing treatment station 111 disposed downstream of the heating zone 20, with respect to the conveyance direction of the continuous filter rod 26. The post-curing treatment station 111 is disposed upstream of the cutting station 24.

The post-curing treatment station 111 is provided to yet further smooth the outer surface of the continuous filter rod 26 after it has been formed in the second duct section 11 b and hardened at the heating zone 20. The filter tow material 16 used to produce the filter rods 29 may comprise many discrete filaments tangled together. Upon formation of the hardened continuous filter rod 28 in the apparatus of the first embodiment, some ends of the filaments may remain upstanding from the outer surface of the filter rod 28 and appear as fine upstanding “hairs”. The post-curing treatment station 111 is therefore intended to provide a further treatment to the continuous filter rod 28 to eliminate these hairs and to give the final discrete filter rods 29 a smoother outer finish.

The post-curing treatment station 111 comprises central passage 112 and electrical heater elements 113. The central passage 112 may be continuous with the duct 11 so that the continuous filter rod 26 passes straight from the outlet 13 of the duct 11 into the central passage 112 of the post-curing treatment station 111.

In use, as the continuous filter rod 26 passes from the outlet 13 of the duct 11, having passed though the heating zone 20 and cured or at least partially cured, it passes into the post-curing treatment station 111. The electrical heating elements 113 heat the filter rod 26 such that the tow material and plasticiser of the outermost surface of the filter rod 26 melts. This also causes any fine hairs upstanding on the outermost surface of the filter rod 26 to also melt. As the hardened filter rod with filled core 28 exits the post-curing treatment station 111, the melted outer surface cools and hardens, forming a thin and smooth outer coating around the continuous filter rod 28.

Following the post-curing treatment station 111, the filter rod 28 is cut into discrete filter rods 129 at a cutting station 24 as per the first embodiment of the apparatus 10 described previously.

FIG. 9 shows a cross-section of the second embodiment of filter rod 129 along the line Z-Z shown in FIG. 8. As with the filter rods 29 of the first embodiment, the filter rods 129 of the second embodiment comprise an outer tubular section 30 with a continuous core 31 of filler material 27. However, the filter rods 129 also include a thin smooth outer coating 130 formed by the melted and hardened tow and plasticiser as described above.

The apparatus of the second embodiment 110 is configured with the conveyance speed of the filter rod 26 and the power of the heating elements 113 such that only a thin outer surface of the filter rod 26 is melted in the post-curing treatment station 111 and heat does not permeate far though the thickness of the filter rod 26. This leaves the majority of the body of the filter rod 26 unaffected by the post-curing treatment. The heating process preferably heats the filter rod 27 to between 100-200 degrees Celsius. This range is optimum for being sufficiently hot to achieve melting of the plasticiser and tow, but not excessively hot as to overheat the filter rod 26 which could cause the material within the body of the filter rod to melt rather than just melt a thin outer layer, which would result in the filter being unusable as the internal melting of the filter rod 26 would render it impermeable.

An apparatus of an alternative embodiment (not shown) may comprise a different configuration of post-curing treatment station 111 disposed downstream of the heating zone 20 and upstream of the cutting station 24. Such alternative configuration of post-curing treatment station may still be provided to smooth the outer surface of the continuous grooved filter rod 26. However, instead of including heating elements to heat and melt the outer surface of the continuous filter rod 26, the post-curing treatment station may comprise one or more spray nozzles within a chamber through which the continuous filter rod 26 is conveyed. In use, the spray nozzles may spray the outer surface of the continuous filter rod 26 with a liquid coating which may harden to form a thin and smooth layer around the continuous filter rod 26. The liquid coating may comprise a plasticiser and may comprise triacetate. Alternatively, the coating may comprise a liquid polymer, such as, polypropylene. Following the alternative configuration of post-curing treatment station, the continuous filter rod 26 may be cut into discrete filter rods at a cutting station as per the first and second embodiments of the apparatus 10, 110 described previously. Such resulting filter rods may be as per the filter rod 129 shown in FIG. 9, having the smooth outer coating 130.

In the apparatus 110 of the second embodiment, the electrical heating elements 113 are described as heating the filter rod 26 such that the tow material and plasticiser of the outermost surface of the filter rod 26 melts, and/or also melting any fine hairs upstanding on the outermost surface of the filter rod 26. However, the invention is not limited to this configuration and method of operation, and the apparatus no may be configured and operated such that the heating elements 113 do not appreciably melt the plasticiser in the outer surface of the filter rod 26, but only soften and physically flatten any upstanding hairs on the filter rod, acting with an “ironing” effect. In such a method of operation, there would not be an appreciable solidified coating formed on the outer surface of the filter rod 26 by melted and hardened tow and plasticiser. However, the final filter would have a smoothed outer surface. In such a method of operation, the temperature of the heating elements 113 may be controlled to be below a temperature that would melt the plasticiser in the filter rod 26, for a given conveyance speed of the filter rod 26 though the post-curing treatment station 111.

In the apparatus 10 of the first embodiment described above, the distal end of the mandrel 17 is disposed downstream of the outlet 13 of the duct 11. This arrangement may advantageously promote the formation of a constant cross-section of filter rod 29 described above. This may result from the filler material 27 only being introduced into the core of the outer tubular section 30 of the filter rod 26 once the duct 11 has reached it narrowest point, so that the filter material 16 of the outer tubular section 30 is fully compressed before the filler material 27 is introduced. Also, in the alternative embodiment in which the distal end of the mandrel 17 is disposed within the duct 11, any outward pressure exerted by the filler material 27 therefore acts upon the compressed filter material 16. However, the invention is not limited to this configuration and the mandrel may alternatively terminate with the distal end in the first, tapering section 11 a of the duct 11.

The post-curing treatment station in of the apparatus 110 of the second embodiment may be formed integrally with the duct 11 or alternatively may be a separate apparatus to the duct 11, and positioned in abutment with the duct 11 so that the continuous filter rod 26 passes directly from the outlet 13 of the duct 11 into the central passage 112 of the post-curing treatment station 111. Yet further, within the scope of the invention, the post curing treatment station 111 may be spaced from the outlet 13 of the duct 11 so the continuous filter rod 26 does not pass immediately into the central passage 112 of the post-curing treatment station after leaving the outlet 13 of the duct 11.

The apparatuses 10, 110 and the methods for filter manufacture avoids use of a conventional garniture belt and plug wrap, thereby avoiding the added complexity and materials of conventional filter road manufacture and therefore the associated costs. Also, a continuous core of filler material is provided in the filter rods 29, 129 in a process that enables high-speed production. Such apparatuses 10, 110 also avoid the need for complex moving mechanisms such as those that may be required in the manufacture of other types of filter which have spaced elements within the filter core. Such mechanisms which may intermittently insert capsules or other elements at regular spacing within a filter core are complex and may require complex control systems to remain accurately in register to ensure the filters produced are consistent and have core elements inserted at the correct spacing. Such mechanisms are therefore costly to produce and maintain.

In the apparatuses 10, 110 described above, the heating zone 20 formed around a section of the duct 11. This may advantageously allow for a compact apparatus configuration. However, the invention is not intended to be limited to such a configuration and in an alternative embodiment, the heating zone 20 may be provided at a separate duct section into which the compressed and extruded continuous filter rod 26 is fed. This latter alternative configuration may advantageously facilitate maintenance of the apparatus, as the heating zone may be separable from the duct section in which the filter material is compressed into a continuous filter rod, enabling easier access and cleaning.

The mandrel 17 may include means to facilitate the filler material 27 being conveyed though the passage 18 from the inlet 18 a to the outlet 18 b. Such means may comprise a compressed air supply coupled to the mandrel 17 to pass compressed air through the passage together with the filler material 27 in a similar manner to how the loose filter tow material 16 is conveyed through the duct 11. The mandrel 17 may include one or more compressed air ports (not shown) extending through a side wall thereof for the supply of compressed air into the passage 18. However, the invention is not limited to such a configuration and the filler material 27 may be drawn through the mandrel 17 by being entrained in the filter tow material 16 conveyed through the duct 11.

The passage 18 of the mandrel 17 is shown as tapering to narrow between the inlet 18 a and the outlet 18 b. However, the invention is not intended to be limited to such a configuration and the passage 18 within the mandrel 17, may be of a constant cross-section along its length.

Furthermore, the outer surface of the mandrel 17 is shown as narrowing from the inlet 18 a end. However, the invention is not limited to such a configuration and the mandrel 17 may be of a constant cross-section along its length.

An advantageous configuration of the apparatuses 10, 110 of the invention comprises the duct 11 tapering to narrow along at least part of the length of the mandrel 17. That is, the distance between the outer surface of the mandrel 17 and the inner surface of the duct 11 reduces along at least a part of the length of the duct 11 in a conveyance direction of the filter tow material 16. This helps compress and at least partially form the filter tow material 16 into the hollow tubular section 30 before introduction of the filler material 27 from within the passage 18 of the mandrel 17.

The apparatuses 10, 110 and methods of the invention described above comprise filler material 27 being introduced into a hollow core of the outer tubular section 30. Although the filler material 27 may be loose, such as a fibrous tow or a granular material, the invention is not intended to be limited to such filler material 27. It is intended in an embodiment of the invention that the filler material 27 may comprise a pre-formed slim continuous filter rod to form the core 31 of the discrete filter rods 29, 129. The filter tow material 16 would then be formed around the pre-formed slim filter rod. Such pre-formed filter rods used as the filler material 27 may be of a size as in known super-slim smoking articles. In such an embodiment, the pre-formed slim filter rod could be conveyed through the apparatus 10, 110 by being pulled though by the conveyance of the surrounding filter tow material 16. In all embodiments, the continuous filter rods 28 may be pulled through the duct 11 by down-stream conveyance drivers (not shown) such as one or more driven rollers, wheels or belts.

An advantageous configuration of the apparatus 10, 110 and method of the invention, and filter rods 29, 129 formed thereby, is that the core 31 and outer tubular section 30 are each formed of a generally homogenous material although each are separate materials. That is, the material of the core 31 is not mixed or blended with the material of the outer tubular section 30 and a clear boundary exists between each part of the filter rod 29, 129. As well as providing a distinctive and clean appearance, this also allows accurate control of the filtering characteristics and performance of the filter rods 29, 129 of the invention. This may advantageously be facilitated by curing or at least part curing of the filter tow material 16 before introduction of the filler material into the core of the tubular filter rod 26. This may be achieved by the distal end of the mandrel 17 being disposed within or downstream of the heating zone 20.

In embodiments of the apparatuses 10, 110 of the invention, the mandrel 17 extends into the heating zone 20. That is, the distal end of the mandrel 17 may be disposed within or downstream of the heating zone 20. For example, the mandrel 17 may extend into the region of the duct 11 within the steam chamber 21 and/or at or beyond at least one of the steam vents 23 formed in the duct 11. This may advantageously enable at least partial curing of the filter tow material 16 forming the outer tubular section 30 before introduction of the filler material 27. This may advantageously help avoid collapse of the outer tubular section 30 during formation. The mandrel 17 extending entirely through the heating zone may advantageously enable improved hardening of the outer tubular section 30 around the mandrel before introduction of the filler material 27 and so provide improved circularity of the core 31.

The apparatuses 10, 110 and methods of the invention described above comprise dry steam at around 170 degrees Celsius being supplied to the chamber 21 to pass through the steam vents 23 and into the filter rod 26. However, the invention is not limited to this specific temperature and the temperature of the dry steam may vary within the scope of the invention. For example, between 100-200 degrees Celsius, and may be between 120-190 degrees Celsius, and may be between 150-180 degrees Celsius. Furthermore, the temperature of the steam may be selected proportional to the amount of plasticiser entrained in the filter tow material 16 and/or also the conveyance speed of the filter tow material 16 through the duct 11.

In an advantageous configuration of the apparatus 10, 110 of the invention, the duct 11 and mandrel 17 are elongate and comprise respective central axes, and the duct 11 and mandrel 17 are co-axial. This may advantageously enable formation of symmetrical and uniform filter rods 29, 129.

In the second embodiment of smoking article 50 described above, the multi-segment filter 51 includes a plug wrap 53 extending around the first and second filter segments 29, 52. This advantageously aids manufacturing as the multi-segment filter may be assembled prior to a separate step in which it is joined to a tobacco rod to make the smoking article. Also, multiple-lengths of multi-segment filters may be produced (e.g. 2-up or 4-up rods) with the filter segments joined by a plug wrap, before being combined with tobacco rods in a separate assembly step to produce smoking articles. However, the invention is not intended to be limited to such a configuration of smoking article, and it is intended that the first and second filter segments 29, 52 may be axially aligned and joined together and to the tobacco rod 41 by the tipping wrapper 42 alone, without also including a plug wrap. This latter configuration may advantageously reduce the number of smoking article assembly steps by the tobacco rod, and first and second filter segments all being combined together with a tipping wrapper in a single assembly process.

As used herein, the term “smoking article” includes smokeable products such as cigarettes, cigars and cigarillos whether based on tobacco, tobacco derivatives, expanded tobacco, reconstituted tobacco or tobacco substitutes and also heat-not-burn products and other nicotine delivery product such as aerosol generation devices including e-cigarettes. The smoking article may be provided with a filter for the gaseous flow drawn by the smoker. In embodiments intended for use with heat-not-burn products and other nicotine delivery products, reference in the description above to “smoke” and “smoke modifying material” should be construed as encompassing other aerosols and inhalants other than smoke and the products of combustion of a material.

In order to address various issues and advance the art, the entirety of this disclosure shows by way of illustration various embodiments in which the claimed invention(s) may be practiced and provide for superior filters, and apparatuses and methods for manufacture of filters. The advantages and features of the disclosure are of a representative sample of embodiments only, and are not exhaustive and/or exclusive. They are presented only to assist in understanding and teach the claimed features. It is to be understood that advantages, embodiments, examples, functions, features, structures, and/or other aspects of the disclosure are not to be considered limitations on the disclosure as defined by the claims or limitations on equivalents to the claims, and that other embodiments may be utilised and modifications may be made without departing from the scope and/or spirit of the disclosure. Various embodiments may suitably comprise, consist of, or consist essentially of, various combinations of the disclosed elements, components, features, parts, steps, means, etc. In addition, the disclosure includes other inventions not presently claimed, but which may be claimed in future. 

1. A filter rod for a smoking article wherein the filter rod comprises a filter segment or may be cut to form individual filter segments, and wherein the filter rod is an extruded hardened tubular element formed from a filter material with entrained cured plasticiser, and a continuous core of filler material provided within the tubular element.
 2. A filter rod according to claim 1 wherein the filter material comprises cellulose acetate tow which is hardened with a plasticiser.
 3. A filter rod according to claim 1 wherein the filter rod does not comprise any outer wrap around the tubular element.
 4. A filter rod according to claim 1 wherein the filler material of the core comprises cellulose acetate.
 5. A filter rod according to claim 1 wherein the filler material comprises a granular aerosol modifying material.
 6. A filter rod according to claim 1 wherein the filler material comprises tobacco or a derivative of tobacco.
 7. A filter for a smoking article comprising a filter rod according to claim 1, and a second filter segment axially aligned with the filter rod and joined thereto by a plug wrap around the filter rod and second filter segment.
 8. A smoking article comprising a tobacco rod and a filter rod or filter according to claim 1 joined to one end of the tobacco rod.
 9. An apparatus for manufacturing an extruded filter rod for smoking articles, the apparatus comprising: a duct having an inlet configured to receive filter tow material and plasticiser, and an outlet, the duct tapering between the inlet and the outlet; a mandrel disposed at least partially within the duct and fixed relative to the duct; wherein the mandrel is hollow and includes an internal passage extending though the mandrel through which a filler material may be conveyed; the passage including an outlet at a distal end of the mandrel though which the filler material may be expelled; and a heating zone configured to heat filter material; the apparatus configured such that filter tow material and plasticiser conveyed through the duct is compressed around the mandrel into a tubular rod, and filler material fed though the internal passage of the mandrel is expelled out of the passage outlet to fill the bore of the tubular rod, and the tubular rod is heated in the heating zone to at least partially cure the plasticiser, to produce a continuous filter rod comprising a tubular rod of hardened filter material with a continuous core of filler material.
 10. An apparatus according to claim 9 wherein the internal passage of the hollow mandrel includes a tapered section which narrows in a direction towards the distal end of the mandrel.
 11. An apparatus according to claim 9 wherein the outer dimension of the hollow mandrel includes a tapered section which narrows in a direction towards the distal end of the mandrel.
 12. An apparatus according to claim 9 wherein a distance between an outer surface of the mandrel and an inner surface of the duct reduces along at least a part of the length of the duct in a direction towards the distal end of the mandrel.
 13. An apparatus according to claim 9 wherein the distal end of the mandrel is positioned downstream of the outlet of the duct.
 14. An apparatus according to claim 9 wherein the mandrel extends entirely through the length of the duct.
 15. An apparatus according to claim 9 wherein the distal end of the mandrel is positioned within the duct.
 16. An apparatus according to claim 15 wherein the mandrel extends into the heating zone.
 17. An apparatus according to claim 16, wherein the duct comprises first and second sections, wherein the first section tapers from the inlet to the second section, and the second section is of constant cross-section, and wherein the distal end of the mandrel is disposed within the second section.
 18. An apparatus according to claim 15, wherein the distal end of the mandrel is disposed within the heating zone.
 19. An apparatus according to claim 9 wherein the mandrel is disposed coaxially with the duct.
 20. An apparatus according to claim 9 wherein the heating zone comprises a steam supply to heat the filter material and plasticiser.
 21. An apparatus according to claim 20 wherein the heating zone includes a steam chamber formed around a section of the duct, and the duct includes steam vents to allow steam supplied to the steam chamber to pass into the duct to directly heat the filter material.
 22. An apparatus according to claim 9 further comprising a post-curing treatment station downstream of the heating zone with respect to the conveyance direction of the extruded continuous filter rod, the post-curing treatment station configured to further smooth the outer surface of the extruded continuous filter rod.
 23. An apparatus according to claim 22 wherein the post-curing treatment station comprises an electrical heater configured to heat the outer surface of the continuous filter rod.
 24. An apparatus according to claim 23 wherein the electrical heater is configured to heat the outer surface of the continuous filter rod to between 100-200 degrees Celsius.
 25. An apparatus according to claim 23 wherein the post-curing treatment station is configured to melt the plasticiser on the outer surface of the continuous filter rod so that the melted outer surface can subsequently set as a smooth finish.
 26. An apparatus according to claim 22 wherein the post-curing treatment station comprises a spray-coating station including a spray nozzle and a source of liquid treatment connected to the spray nozzle to spray the liquid treatment onto the outer surface of the continuous filter rod to form a smooth outer coating.
 27. An apparatus according to claim 26 wherein the liquid treatment sprayed from the spray nozzle comprises a plasticiser, and may comprise triacetate.
 28. An apparatus according to claim 9 further comprising a cutting station configured to cut the continuous extruded filter rod into discrete filter rods.
 29. A method of manufacturing extruded filters for smoking articles, the method comprising feeding filter tow material and plasticiser into an inlet of a duct, the duct tapering between the inlet and an outlet, conveying the filter tow material through the duct and around a hollow mandrel disposed at least partially within the duct and fixed relative to the duct, such that the filter material is compressed into a tubular rod, conveying a filler material along an internal passage extending through the hollow mandrel, expelling the filler material from an outlet of the internal passage at a distal end of the mandrel to fill the bore of the tubular rod with the filler material, and heating the tubular rod to at least partially cure the plasticiser to produce a continuous filter rod comprising a tubular rod of hardened filter material with a continuous core of filler material.
 30. A method according to claim 29 comprising expelling the filler material from the internal passage outlet at the distal end of the mandrel downstream of the outlet of the duct.
 31. A method according to claim 29 comprising expelling the filler material from the internal passage outlet at the distal end of the mandrel within the duct, upstream of the duct outlet.
 32. A method according to claim 29 comprising heating the filter material and plasticiser in a heating zone of the apparatus using steam.
 33. A method according to claim 32 comprising heating the filter material in the heating zone to at least partially cure the plasticiser before filling the bore of the tubular rod with the filler material.
 34. A method according to claim 29 comprising compressing the filter tow material to at least partially form the tubular rod before filling the bore of the tubular rod with the filler material.
 35. A method according to claim 29 comprising providing cellulose acetate tow as the filler material.
 36. A method according to claim 29 comprising providing a pre-formed filter rod through the mandrel as the filler material.
 37. A method according to claim 29 comprising providing tobacco as the filler material.
 38. A method according to claim 29 further comprising performing a post-curing treatment on the continuous filter rod to provide the continuous filter rod with a smoother outer surface than the surface texture present when expelled from the heating region.
 39. A method according to claim 38 wherein the post-curing treatment comprises heating the outer surface of the continuous filter rod with an electrical heater and smoothing the outer surface.
 40. A method according to claim 39 wherein the post-curing treatment comprises heating the outer surface sufficiently to melt the plasticiser on the outer surface of the continuous filter rod and subsequently setting the melted outer surface as a smooth finish.
 41. A method according to claim 40 comprising heating the outer surface of the continuous filter rod to between 100-200 degrees Celsius.
 42. A method according to claim 38 wherein the post-curing treatment comprises spray-coating a liquid treatment onto the outer surface of the continuous filter rod to form a smooth outer coating.
 43. A method according to claim 42 comprising spraying a plasticiser, which may comprise triacetate, onto the outer surface of the continuous filter rod.
 44. A method according to claim 29 further comprising cutting the continuous extruded filter rod into discrete filter rods. 